1. Field of the Invention
The present invention relates to a thin film transistor array substrate, for example, for use in a liquid crystal display device, and particularly, to a thin film transistor array substrate for use in a liquid crystal display device in a fringe field switching mode, and to a manufacturing method of the thin film transistor array substrate.
2. Description of the Background Art
A liquid crystal display device in a fringe field switching (FFS) mode is a display device that performs display by applying a fringe field to a liquid crystal sandwiched between two substrates opposite to each other. A pixel electrode and a counter electrode (common electrode) are formed of transparent conductive films, and accordingly, an aperture ratio and a transmittance in the liquid crystal display device in the FFS mode can be increased more than those of a liquid crystal display device in an in-plane switching (IPS) mode.
In such a conventional liquid crystal display device in the FFS mode, in order to manufacture a thin film transistor (TFT) array substrate, there are required at least six photolithography steps of transferring respective patterns of: (1) a counter electrode; (2) a gate electrode; (3) a semiconductor film; (4) a source/drain electrode; (5) a contact hole; and (6) a pixel electrode, and there is a problem that manufacturing cost is increased in comparison with a liquid crystal display device in a TN (Twisted Nematic) mode capable of manufacturing the TFT array substrate by five photolithography steps. Meanwhile, for example, Japanese Patent Application Laid-Open No. 2010-191410 proposes a technology for forming the liquid crystal display device in the FFS mode by five photolithography steps.
In a manufacturing method of the liquid crystal display device in Japanese Patent Application Laid-Open No. 2010-191410, in order to set the number of photolithography steps for the TFT array substrate in the FFS mode at the same number (five) as the number of photolithography steps for the TFT array substrate in the general TN mode, a configuration is adopted, in which the transparent conductive film is arranged on a metal film pattern, which becomes a source wire, without an insulating film being interposed therebetween.
The TFT array substrate formed by the manufacturing method in Japanese Patent Application Laid-Open No. 2010-191410 forms a structure in which the transparent conductive film, which becomes a pixel electrode, remains not only on a forming region of the pixel electrode but also on a source wire adjacent to the forming region. Therefore, there is a problem that a cross talk point defect, which is caused by the fact that the pixel electrode and the source wire connect to each other by a pattern defect of the transparent conductive film, is prone to occur.
Repair of the cross talk point defect is performed by cutting or removing (laser repair cut) the pattern defect of the transparent conductive film, which remains so as to connect the source wire and the pixel electrode to each other, by using a laser repair device after patterning of the pixel electrode. Alternatively, in some case, the repair is performed by cutting or removing the pattern defect of the resist pattern, which is formed so as to lie astride the source wire and the forming region of the pixel electrode, by using the laser repair device after formation of a resist pattern that becomes a mask for patterning the pixel electrode. The pattern defect of the resist pattern is cut or removed, whereby an occurrence of the pattern defect of the transparent conductive film can be avoided. Note that, in some case, the pattern defect of the resist pattern is formed of a foreign object other than such a resist material.
By the laser repair device, a position of the cross talk point defect (that is, a position of the pattern defect of the transparent electrode or the resist pattern) cannot be specified. Therefore, it is necessary to specify the position of the cross talk point defect by an inspection (pattern defect inspection) performed by using a pattern defect inspection device or an optical inspection device. As a method of the pattern defect inspection, such a method is general, in which light is applied onto pixel patterns arranged periodically, pieces of reflected light thereof are compared with one another at the same spot of three or more pixel patterns, and a spot different in brightness from those of other pixel patterns is detected as the position of the pattern defect.
In the above-described pattern defect inspection, it is easier to detect the pattern defect as a brightness difference of the reflected light appears to a larger extent between a spot of a normal pattern and the spot of the pattern defect. However, in the TFT array substrate in Japanese Patent Application Laid-Open No. 2010-191410, the spot of the normal pattern between the source wire and the pixel electrode forms a structure in which only an insulating film is formed on the substrate, and the spot where the cross talk point defect occurs forms a structure in which the insulating film and the transparent conductive film are formed on the substrate. Therefore, such a large brightness difference is not generated in the reflected light between the spot of the normal pattern and the spot of the cross talk point defect, and it is difficult to detect the pattern defect. If the pattern defect remains without being detected, then the cross talk point defect occurs as a result.